Electrical contact



Nov. 7, 1961 P. F. HAYNER 3,008,023

ELECTRICAL CONTACT Filed April 1, 1960 INFORMATION |9 UTILIZING MEANS INFORMATION SOURCE INFORMATION SOURCE INFORMATION SOURCE IO c INFORMAT ON SOURCE Fig.l

INFORMATION SOURCE INFORMATION SOURCE Fig.2 Fig.3

Paul F. HOyner INVENTOR 3,.W8fl23 ?atenterl Nov. 7, 1961 fiice Ware Filed Apr. 1, 1960, Ser. No. 19,302 1 Claim. (Cl. 200-452) This invention is directed in general to electrical contacts and is more specifically directed to a contact for making sliding connection with one or more other contacts.

A prevalent problem in the electrical field is the need for making electrical connection between stationary and moving contacts. Probably the most common example of this need is found in an electrical motor where connection must be made between an external stationary source of power and a moving armature. In this case the connection is made through a commutator which usually comprises a rotary set of copper or silver contact surfaces connected to armature windings and a set of stationary carbon brushes coupled to the external power source and in sliding contact with the moving copper or silver surfaces. Usually this arrangement for making contact between moving and stationary objects is satisfactory. However, when commutation of the type just described is employed to sample electrical information in a large number of circuits over a short period of time, the switching action, apparently due to the inherent noisiness of carbon brushes, introduces an undesirable amount of noise into the information circuits. The carbon granule accumulation as a brush wears is also a source of trouble. It is desired to reduce this noise and eliminate troublesome granules.

It is therefore an object of the present invention to provide a new and improved electrical contact for making Sliding connection with another contact.

It is also an object of the present invention to provide a new and improved electrical contact which is extremely simple to manufacture.

It is a further object of the present invention to provide a relatively noise-free electrical contact.

It is a still further object of the present invention to provide a new and improved electrical contact for making substantially frictionless sliding connection with another contact.

It is a still further object of the present invention to provide a new and improved electrical contact for making a substantially erosionless sliding connection with another contact.

In accordance With the present invention an electrical contact for making a sliding connection with another contact comprises a body having terminals for connection to an electrical circuit and a cavity electrically connected to the terminal. Mercury is deposited in the cavity sufiicient to fill the cavity and form a convex meniscus above the surface of the body to provide a surface of mercury for making sliding connection with the other contact.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claim.

In the drawing:

FIG. 1 is a perspective, somewhat diagrammatic, representation of a system using a multi-contact switch having an electrical contact in accordance with the present invention;

FIG. 2 is a more detailed view of the moving electrical contact of FIG. 1; and

'10 FIG. 3 is a cross-sectional v1ew of the electrical contact represented in FIG. 2.

Description and explanation of operation of the electrical contact of FIGS. 1, 2, and 3 FIG. 1 represents an electrical contact for making sliding connection with a plurality of contacts, more specifically, representing a rotating switch or commutator for coupling sources of information to an information utilizing means in accordance with some programming procedure. The system of FIG. 1 includes a plurality of information sources llla-ltlz, inclusive, the number of sources being determined primarily by the diversity of information desired and secondarily by the limitations of a switching member to be described hereinafter. The information sources llla10z, inclusive, may be, for example, strain gauges positioned at different parts of an apparatus under test, such as a missile, for determining the strain on different parts. The information sources 161240 also represent a plurality of radio-frequency amplifiers for receiving signals in different frequency spectra, as might be utilized, for example, in a panoramic receiver. The information sources are electrically and individually connected to different terminals on a stationary member ll of a switch or commutator 12 For example, the information source 10a is connected to a terminal 13a on the member 11. The switch or commutator 12 includes a rotating member 14 mechanically coupled through a shaft 15 to a driving motor 16. The rotating member 14 comprises a body 17 more clearly represented in FIGS. 2 and 3, having a terminal 18 for connection to an electrical circuit, specifically for connection to an information utilizing means 19'. The wiring for connection to the means 19 is arranged to pass through the center of the shaft 15 and is coupled by means of a slip ring to the means 19. The information utilizing means may be, for example, a cathode ray oscilloscope, some form of permanent recording device, or in the case of a panoramic receiver the audio and sound reproduction circuits of such receiver.

Referring again to FIGS. 2 and 3, the body 17 also in cludes a cavity 20 electrically connected to the terminal 18 by means of a conductive strip 21. The conductive strip 21 may comprise a printed circuit strip or a physical Wire connection of the cavity 24 and terminal 18. Of course, such strip is not needed if the body 17 is of conductive material. A deposit of mercury 22, most visible in FIG. 3, is placed in the cavity 26. The quantity of mercury is sufiicient to fill the cavity and to extend slightly above the upper face of the body 17 to form a convex meniscus above the surface. The meniscus provides substantially frictionless and erosionless contact with the stationary terminals 13a-l3z on the member Ill.

The system of FIG. 1 operates in a conventional manner, periodically to couple the information sources lua lllz, inclusive, to the information utilizing means 19. The motor 16 rotates the member 14- to cause the convex meniscus of the mercury 22 to contact each one of the stationary contacts 13tz13z, inclusive, for a short period. It should be apparent that the meniscus of mercury provides a clean noiseless and frictionless contact, thereby introducing relatively little noise in the switching operation. Additionally, it has been found that the make-andbreak transients resulting from the mercury contact are cleaner and neater than those available when employing carbon brushes.

Though the simple commutator arrangement described above is normally satisfactory for most purposes, if extremely minute potentials are employed, sometimes un controlled coatings on the surfaces of the contacts 13a- 132 are sufficient to introduce wide variations in resistance thereby causing the switching to be noisy. In accordance with a form of the present invention, this deficiency is eliminated by operating the commutator in vacuum or in an inert gas after all contacts have been thoroughly cleaned.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claim to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is: claimed is:

An electrical contact arrangement comprising,

a stationary switch means,

said switch means having a plurality of discrete electrical contacts thereon,

a plurality of information sources,

each of said information sources being individually connected to a corresponding one of said electrical contacts,

a rotating member,

said rotating member having a substantially elongated body,

said elongated body having two parallel side portions,

one of said side portions having a cavity located thereon,

a deposit of mercury in said cavity sufiicient to fill said cavity and form a convex meniscus above the surface of said side portion,

said rotating member being positioned so that movement of said member causes said convex meniscus to respectively contact said discrete electrical contacts,

means for rotating said rotating member with respect to said plurality of discrete electrical contacts,

information utilizing means,

said information utilizing means being connected to said mercury in said cavity whereby said information utilizing means will receive information from said information sources upon movement of said rotating member and upon contact of said mercury with said discrete electrical contacts.

References Cited in the file of this patent UNITED STATES PATENTS 762,0'4'0 'Freese June 7, 1904 2,278,846 Goerth Apr. 7, 1942 2,647,975 Jack et al Aug. 4, 1953 

